3-Dimensional Quantitative Measurement of the Geometric Changes in Steam Generator Tubes Using a Diagnostic Eddy Current Probe (D-Probe)

Occurrences of the stress corrosion cracking in steam generator tubes of nuclear power plants are closely related to the residual stress existing on the region of geometric change, that is, expansion transition, u-bend, ding, dent, bulge, etc. Therefore, the information on the location, type and quantitative size of the geometric anomaly existing in the tube is prerequisite to the activity of non destructive inspection for the alert detection of earlier crack and the prediction of further crack evolution. In this paper, a newly developed eddy current probe, which has been equipped with the simultaneous dual functions of the crack detection and the 3-dimensional quantitative profile measurement, is introduced. The proof of the probe performance including the accuracy of profile measurement and the applicability of the probe to the plant inspection is provided through the setting-up of the calibration procedure, and the comparison of the quantitatively measured data with those from the laser profilometry for the steam generator tube samples of geometric anomalies with various type and size